#define _CRT_SECURE_NO_WARNINGS 1

class Solution {
public:
    vector<string> ret;
    string path;
    string hash[10] = { "", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz" };
    vector<string> letterCombinations(string digits)
    {
        if (digits.size() == 0)return ret;
        dfs(digits, 0);
        return ret;
    }

    void dfs(string& digits, int pos)
    {
        if (path.size() == digits.size())
        {
            ret.push_back(path);
            return;
        }
        for (int i = 0; i < hash[digits[pos] - '0'].size(); i++)
        {
            path.push_back(hash[digits[pos] - '0'][i]);
            cout << hash[digits[pos] - '0'][i] << endl;
            dfs(digits, pos + 1);
            path.pop_back();
        }
    }
};